Means and method for making seamless pipe elbows



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MEANS AND METHOD FOR MAKING SEAMLESS PIPE ELBOWS Filed Nov. 8, 1945 2 Shaecs-Sheet l I: A L

41 (ILL \2 r INVENTOR U 4: WALTON s. ROBlNSON ATTORN EY .My 17, W51 W. s. ROBINSON MEANS AND METHOD FOR MAKING SEAMLESS PIPE ELBOWS 2 Sheets-Sheet 2 Filed Nov. 8, 1945 INVENTOR.

WALTON S. ROBINSON Patented July 17, 1951 MEANS AND METHOD FOR MAKING SEAMLESS PIPE ELBOWS Walton S. Robinson, Westfield, N. .J

Application'November 8, 1945, Serial No. 627,347

4'Claims. l

My improvements relate'to means and a meth-1 otl of making wrought seamless elbows such as are used in industrial piping, but they may be adapted for other purposes. They are based on the art of deep drawing sheet or plate as distinguished from the art of bending or forming tubing. The novel features involve primarily drawing a curved elbow shapeds'hellfrom a'straight or cup shaped shell in one or'moredrawing operations.

Its objects are, among others, to produce instrumentalities and a method which may be performed thereby for cold drawing such elbows from sheet and plate .of various thicknesses, analyses and composition, insuring uniform gauge and strength throughout, smooth regular surfaces and freedom from flaws, and to substantially lower the cost of manufacturing seamless elbows, from alloys unsuitable for hot working methods, and from light gauge materials generally.

Other objects and advantageswill appear from the following specifications and the drawings referred to herein.

The improvements are illustrated in the accompanying drawings which show an exemplary embodiment of the apparatus phase of the invention and by which the method or processmay be performed. In the said drawings,

Fig. 1 comprises a series of diagrammatic illustrations of the steps by which is produced the cup-shaped blank from which the elbow is formed, drawn on a reduced scale;

.Fig. 2 is alike series of diagrams showing the successive steps in the operations'of drawing the elbow from the blank;

Fig. 3 is a transverse; medial vertical section of the forming ring'die of Figs. .4, and 6, on a larger scale than Figs. 4 and 5;

Fig. 4 is a vertical medial section of the apparatus with the cup-like blank in its ante-operation position therein but with the die in its postoperation position;

Fig. 5 is an end elevation of the apparatus in Fig. 4;

Fig. 6 is a detached detail on the enlarged scale of .Fig. 3 of the forming horn or mandrel with blank and forming ringrthereon shown in longitudinal vertical medial section, as in Fig. 4. y

The curved mandrel :or born I is fixedly mountedon the upright member l -mounted in an hydraulic press (not shown) by having its reducedend .3 passed into an aperture l thereof and secured by screw bolts 5 threaded -thereinto, passing through the block I andpressing the shoulder 6 against the inner side of the upright member '2. In this manner it is firmly but demountably secured and held accurately in its upwardly extending position, but may be dismounted and replaced by mandrels of different sizes to be employed in forming elbows or bends of other diameter orform.

The forming ring die 8 is mounted between upwardly extending arms 9 of the frame member 2 to swing up and down through an are on the curved mandrel I, passed through its central aperture ID, by the pivot bar H fixed strongly thereto and mounted in said arms in bearings between them and the blocks I2, secured to said arms by machine screws l3, so that the said forming ring may be removed and replaced.

The ring 8 is so pivoted that the are described by the margins of its central aperture are parallel to the arc of mandrel l throughout the circumferences of these parts and both arcs are formed by radii drawn from a common center, which is the center of the pivot II. The shell forming surfaces of these margins must also be at all times in close and unvarying proximity to the adjacent surfaces of the mandrel. However, as the radius of longitudinal curvature of the mandrel increases constantly with the distance of its surface from the pivotal center it is necessary that the thickness of the forming ring 8 shall be increased outwardly from its pivot and its curvature varied, to accommodate the said margin to the curve of the mandrel and of the cylindrical elbow-shaped shell formed thereon by pressure between these two dies. Otherwise the parts would bind and uneven pressure on the blank would occur, resulting in an imperfect elbow. This formation of the ring is shown in Figs. 3, 4 and 6 and particularly in Fig. 6, in which the annular upper and lower rounded portions I l and I5 of the ring margin are seen to be turned outwardly and flared to correspond with the increasing thickness of the ring die 8 which at its extreme outer part 8' is approximately 1 times the thickness of the part at its pivot. These rounded portions are also separated by a relatively flat portion l'6 flaring outwardly.

The upper rounded portion [4 of the ring or collar 8 is the portion by which final form is given to the elbow formed by the dies from the cup-like blank (shown at D, Fig. 1 and at 2|, Figs. 4 and 6-), and the lower rounded portion l5 with the intermediate flat portion [6 shrink or contract the blank on the mandrel or form I and prepare it for this final formation. The forms of blanks shown, however, maybe varied in size andform to a certain extent and some of them-for instance the blank Dmay be omitted and the blank E produced from C, which may be curved, also F may be the final finished form.

The forming ring 8 is operated by the power arms l9, pivotally connected with the ring by trunnions 20 at the outer part of the latter, and supplied with power preferably by hydraulic means and with means (not shown) for raising it and the ring after each power stroke.

The cup-like blank 2! is drawn, as shown in Fig. 1, from a flat sheet of metal A, in any suitable manner, by first drawing a shallow cup B, then drawing it deeper and then trimming its open end and cutting it off on an angle corresponding approximately to the radius of the mandrels are, if desired, as indicated at C and D, Fig. 1. This blank is then placed on the mandrel with its closed end 22 receiving the upper end of the mandrel, as shown in Figs. 4 and 6, but not necessarily centered thereon, since the greater part of the sheet metal of the blank will be employed in forming the portion of the elbow outside its medial diameter (see Fig. 6). The blank is then drawn out by the action of the ring operating over the mandrel to the desired reduced diameter, increased length and curved form, as indicated at E and F, and the flattened closed end 22 then out off, to form the finished elbow, as indicated at G, in Fig. 2. The upper end of the mandrel is disposed at an angle to its mean length and is disposed approximately in a plane radial to the central point of the arcs described by the mandrel and ring.

When the diameter of the finished elbow is to be smaller than can be obtained on the first draw over the curved horn it may be stripped from this horn and redrawn with smaller dies of a similar nature to those illustrated in Fig. 6. When a blank is to be drawn further after the first drawing it is preferable to employ a horn with a convex upper end so as to have the closed end of the blank rounded instead of flat after the first drawing, as that facilitates the action and operation of the dies at the beginning of the second drawing.

Due to the fact that the diameter of the cupshaped blank is substantially reduced in the drawing operation the thickness of the sheet metal is decreased little, if any, and its original strength and uniform gauge is therefore substantially maintained, while its smooth surfaces and freedom from flaws are preserved. It should be understood, that dies of varying diameter and curvature may be employed and that reducing elbows may be produced by first drawing the entire blank to a certain diameter and then drawing a part of its length to a smaller diameter, and that such workas well as other operationsmay be performed on the same apparatus by different dies curved and operating on radii drawn from the same pivotal center, but located at a different point vertically.

As the dies are primarily employed for forming a curved elbow-shaped shell they differ essentially from all dies for forming straight tubes or shells and require that the section of the movable die nearest the axis or pivot shall have an increased fiare or taper on its drawing surface in order to clear the inside radius of the horn or mandrel and also to allow sufficient clearance for the advance portion or skirt of the tubular blank to draw down to the land or smallest point on the drawing surface, and the angle of the flare must be reduced gradually and uniformly, correspending with the cross sectional curvature of the '4 l mandrel. On the outside or point farthest from the axis, however, the fiared portion of the drawing surface must also be made longer in order to allow the metal of the straight blank or shell to first bear on the drawing surface and then flow smoothly to the smallest or land point. This is accomplished by making the die substantially wedge shaped, providing a greater angle at the part nearest the axis and a lesser angle at the part farthest from the axis. The curvature of the drawing surface of the movable die must also change gradually to meet these conditions, and to this end the outwardly diverging and tapering rounded portions 44 and I5 with the flaring intermediate fiat portion [6 between them are provided.

The details of the power means and its application to the dies are not a part of the present improvements and any suitable means for that purpose may be employed. Thus the power arm shown in the drawings, which is provided with a flexible connection with the power unit to permit the necessary lateral movement to accommodate it to the arcuate movement of the die 8, may be replaced by a rack and gear with the gear describing the same are as the part of the die to which it is attached, and still other means may be employed for the purpose.

The improvements may be embodied in and the method or process practiced by other forms of apparatus than the exemplary embodiment herein shown and described; and blanks, elbows and.

bends having other than strictly cylindrical crosssection may be employed and produced such as elliptical or substantially rectangular pipes. The language of the claims is therefore not to be construed as being limited to such details.

Automatic means may be employed for stripping the drawn blank-which is indicated by dotted lines in Fig. 4from the mandrel, but such means are not a part of the present improvements, and it will be understood that the dies and blank will be sufficiently lubricated before the drawing operation begins.

In the employment of the apparatus to practice the method or process the cup-like blank is placed over the upper end of the mandrel with its closed end receiving and resting upon the said end and thus supporting the blank during the drawing operation. The blank, however, is positioned with the center of its cap or closure outside the longitudinal axis of the mandrel, to allow for the extra metal needed on the longer radius of the dies and formed elbow. The aperture of the movable die is then passed over the cap of the blank and the top of the mandrel and the said die then forced down to a point below the bottom of the blank, when the blank may be removed by suitable strippers. In this movement of the die the blank is first drawn in by the beveled or tapered part of the aperture margin and fed or caused to flow to the land or most contracted space between the die and mandrel, which is between the rounded portion I4 and the surface of the said mandrel and corresponds approximately to the gauge or thickness of the sheet metal of the blank,

where it is squeezed into its final shape con- It will be understood that the number, size and shape of the blanks shown in Figs. 1 and 2 are merely illustrative and that blanks of other form and size may be produced and used in the initial stages, and also that the mandrel and ring die may be varied in length and curvature to produce variations in the diameter, gauge and curvature of the elbows.

What I claim is:

1. In a device of the character described, a curved arcuate horn and a die having an aperture therein slightly larger than said horn but with a circumferential wall of said aperture concentric with the adjacent circumferential surfaces of said horn, said parts being respectively of substantial length and thickness and mounted for arcuate movement one with respect to the other with the said horn surrounded by the said die, the walls of said aperture being flared away from the circumferential portion closest to said horn and the said flare being more abrupt at the arc of shorter radius of the horn than at its arc of greatest radius and tapering from the former to the latter, the construction and arrangement being such that when a hollow metal blank is inserted between said horn and die and one passed over or through the other the metal of said blank will be crowded away from said shorter radius and distributed substantially uniformly throughout its circumference while the length of said blank is extended and its diameter reduced.

2. In a device of the character described, a rigid curved arcuate mandrel and a die having an aperture therein slightly larger than said mandrel but with a portion of the circumferential wall of said aperture approximately concentric with the adjacent circumferential surfaces of said mandrel, said parts being respectively of substantial length and thickness and mounted for arcuate movement one with respect to the other with the said mandrel surrounded by the said die, the walls of said aperture being flared. away from the circumferential portion closest to said mandrel and the said flare tapering between the arc of shorter radius and the arc of greater radius of the mandrel, the construction and arrangement being such that when a hollow metal blank is positioned between said mandrel and die and one passed over or through the other, the metal of said blank will be moved away from said shorter radius and distributed approximately uniformly throughout its circumference while the length of said blank is extended and its diameter and gauge or thickness reduced.

3. In a device of the character described, a fixed curved arcuate mandrel and a die having an aperture therein slightly larger than said mandrel but with apart of the circumferential wall of said aperture approximately concentric with the adjacent circumferential surfaces of said mandrel, said parts being respectively of substantial length and thickness and the die mounted for arcuate movement with respect to the mandrel with the said mandrel surrounded by the said die, the walls of said aperture being flared away from the circumferential portion closest to said mandrel and the said flare tapering from the arc of shorter radius to the arc of greater radius of the mandrel, the construction and arrangement being such that when a hollow metal blank is positioned between said mandrel and die and the die passed over the mandrel the metal of said blank will be moved away from said shorter radius and distributed approximately uniformly throughout its circumference while the length of said blank is extended and its diameter and gauge adjusted.

4. The herein disclosed method of forming curved tubular elbows or bends which includes the steps of forming a tubular blank, positioning said blank on a curved mandrel or form of greater length and lesser diameter than the blank, compressing and drawing the blank and thereby conforming it to the shape, diameter and length of the mandrel by applying thereto external longitudinal and circumferential pressure applied thereto on lines converging toward the external surfaces of the mandrel and finally compressing the metal of the blank against said mandrel along a circumferential zone which is flared outwardly from the arc of smaller to the arc of greater radius of the mandrel and blank and thereby distributing the metal of the blank outwardly over its circumference and compensating for its outwardly increasing area.

WALTON S. ROBINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,162,374 Koenig Nov. 30, 1915 1,598,893 Taylor Sept. 7, 1926 1,962,469 Taylor June 12, 1934 1,962,510 Taylor June 12, 1934 

